British researchers have come up with a mathematical equation to predict happiness, and it's a lot more complex than beach vacation + winning the lottery = glee. In fact it looks like this:

But let's try plain English. Researchers from University College London conducted an experiment involving rewards and expectations, and concluded that expectations, more than rewards, can impact moment-to-moment happiness -- and can even influence our moods before we learn the outcome of a decision. So, for example, you make plans to see " Guardians of the Galaxy." Your positive expectations of the experience (and reviews suggest you have cause for optimism) may spike your mood as soon as you mark the plan in your calendar.

"We expected to see that recent rewards would affect moment-to-moment happiness but were surprised to find just how important expectations are in determining happiness," researcher Robb Rutledge, a cognitive and computational neuroscientist with UCL's Wellcome Trust Centre for Neuroimaging, said in a statement. "In real-world situations, the rewards associated with life decisions such as starting a new job or getting married are often not realized for a long time, and our results suggest expectations related to these decisions, good and bad, have a big effect on happiness."

The researchers -- who just published their research in the journal PNAS -- presented 26 subjects with a decision-making task involving monetary gains and losses and repeatedly asked them to report their happiness levels along the way. The scientists then measured participants' brain activity using functional MRI and built a computational model that linked self-reported happiness to recent rewards and expectations.

They followed up by testing their model on more than 18,000 participants in a game within The Great Brain Experiment, a mobile app developed at UCL that uses "gamified" neuroscience experiments to address scientific questions on a scale that wouldn't be possible using more traditional approaches. The scientists said their same equation could be used to predict subjects' happiness while playing the smartphone game, even though they could only win points and not money.

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Though it's clear that economic and sociological factors such as wealth and social support -- and, possibly even genetics -- can impact overall happiness, the UCL researchers wanted to take it down to the micro scale and focus more on how the cumulative influence of events in daily life add up when it comes to feeling good.

What use are the findings? Like other studies in the increasingly active field of happiness research, they could be used to help governments formulate policy that encourages citizens' well-being. The UCL researchers say their study is particularly relevant to the UK following the 2010 launch of the National Wellbeing Programme and subsequent annual reports by the Office for National Statistics on measuring national well-being.